1. Field of the Invention
The present invention relates to a focusing apparatus for a camera and, more particularly, to a focusing apparatus for a camera, which can switch automatic and manual focusing operations.
2. Related Background Art
A camera comprising an automatic focusing apparatus has a distance-measurement device for measuring a distance to an object and outputting a distance-measurement signal according to the measurement result, and a lens driving device for moving an imaging lens along an optical axis for focusing. The imaging lens which is moved along the optical axis in accordance with a shooting operation is locked by a locking member which is operated in response to the distance-measurement signal and determines the position of the lens along the optical axis. In some cameras with the automatic focusing apparatus of this type, an object distance can be manually set in advance in the case of imaging of an unclear object with low constrast or fine patterns whose distance is difficult to measure, imaging under bad conditions where dust or water droplets become attached to the distance-measurement device, or underwater imaging where projection light for distance measurement is considerably attenuated and distance measurement may be rendered impossible.
A camera with an automatic focusing apparatus which can manually set a distance is disclosed in, e.g., Japanese Patent Application Laid Open No. 61,523/1979. In this known camera, in order to lock an imaging lens which is movable along the optical axis at a position along the optical axis corresponding to an object distance, another locking member for manually adjusting a distance is arranged in addition to the locking member for automatic focusing. In the case of the manual distance adjustment, the imaging lens is locked at a predetermined position by the locking member for the manual adjustment. In the case of automatic adjustment, after the imaging lens is moved to a reset position, the imaging lens is moved from the reset position and is locked by the locking member for the automatic focusing to allow its focusing operation. For this purpose, when a focusing mode is switched from the manual to automatic mode, moving means for moving the imaging lens to the reset position is necessary. On the other hand, when the focusing mode is switched from the automatic to manual mode, canceling means for canceling the locking of the imaging lens at the reset position must be arranged. This results in a complex arrangement, and requires an increase in the number of parts.